Increased hippocampal excitability and altered learning dynamics mediate cognitive mapping deficits in human aging

Abstract

Learning the spatial layout of a novel environment is associated with dynamic activity changes in the hippocampus and in medial parietal areas. With advancing age, the ability to learn spatial environments deteriorates substantially but the underlying neural mechanisms are unknown. Here, we report findings from a behavioral and a fMRI experiment where older and younger adults performed a spatial learning task in a photorealistic virtual environment. We modeled individual learning states using a Bayesian state-space model and found that activity in retrosplenial cortex/parieto-occipital sulcus and anterior hippocampus did not change systematically as a function learning in older compared to younger adults across repeated episodes in the environment. Moreover, effective connectivity analyses revealed that the age-related learning deficits are linked to an increase in hippocampal excitability. Together, these results provide important insights into how human aging affects computations in the brains navigation system, highlighting the critical role of the hippocampus.